The present invention relates to a method making it possible to measure the position of a mobile structure, in particular, a structure of an aircraft fuselage.
An aircraft fuselage is, in a known way, constituted by the assembly of a plurality of structures such as the nose section, the rear section or various cylindrical sections.
The step of assembling two structures comprises positioning the structures on supports and bringing a structure mounted on a mobile support towards another structure mounted on a fixed support until the two structures are joined. The structures are then definitively fixed to each other, for example by riveting.
During its displacement, the position of the mobile structure is constantly measured in order to ensure the correct progress of the assembly step.
A photogrammetric method is used to carry out these measurements. Such a method makes it possible to construct a cloud of points in three dimensions of the mobile structure by acquiring, via several cameras, images taken at different angles, of a plurality of targets distributed over the whole of the structure and by using the parallax obtained between the different images acquired. The cloud of points makes it possible to give the respective position of the structure in a given set of reference axes. Each target, such as described notably in the document US 20070153297, comprises an optical code unique to the target. The target is reflective when it is illuminated by a laser projector so that it can be detected by the cameras.
The use of such targets for measuring the position of a structure slows down production rates because operators have to install the plurality of targets (for example of the order of 200 of them for a nose structure) solely for the measurements and then they have to remove them once the measurements have been taken.